While rescuers scramble to dig out any remaining survivors from a weekend tornado that killed 116, residents in Joplin, Missouri, are bracing for the possibility of more tornadoes on Tuesday.

"There's no way to figure out how to pick up the pieces as is," Sarah Hale, a lifelong Joplin resident, said Tuesday. "We have to have faith the weather will change."

The National Weather Service warned there was a 45% chance of another tornado outbreak -- with the peak time between 4 p.m. and midnight Tuesday -- over a wide swath including parts of Texas, Oklahoma, Arkansas, Nebraska and Missouri.

Joplin is also in the area.

But if Monday's rescue efforts are any indication, even severe weather might not hamper the search for survivors.

City Manager Mark Rohr told reporters that more than 40 agencies are on the ground in the southwest Missouri city, with two first responders struck by lightning as they braved relentless rain and high winds searching for survivors.

By Monday night, they found 17 people alive. But many, including Will Norton, remain missing.

The 18-year-old was driving home from his high school graduation Sunday when the tornado destroyed the Hummer H3 he and his father were in.

"We were in a separate car. We were about 30 second in front of them, one block," Norton's sister, Sara, told CNN's Anderson Cooper. "My dad called and he said, 'Open the garage door.' ... And then I just heard him say, 'Pull over, Will. Pull over.' And then they started flipping."

"My dad said -- when my dad gained consciousness, he said that he saw my brother -- his seat belt snapped and he was ejected through the sunroof," she added.

The family has been tracking a "Help Find Will Norton" Facebook page and pursuing leads on his whereabouts.

Norton's aunt, Tracey, said the family received a tip that the teen was listed on a local hospital's emergency room roster -- but she's not sure where he is now.

"They transferred him, but we're not sure where he was transferred," the aunt said. "When he was transferred, he was alive. We don't know anything other than that."

The tornado that carved through the city of about 50,000 on Sunday tied for the single deadliest twister to ever hit American soil since the National Weather Service began keeping records 61 years ago. An equally deadly tornado struck Flint, Michigan, on June 8, 1953.

"Everybody's going to know people who are dead," said Zach Tusinger, who said his aunt and uncle died in the Joplin tornado. "You could have probably dropped a nuclear bomb on the town and I don't think it would have done near as much damage as it did."

With crews still sifting through rubble, the death toll could continue to climb.

"I think the more time that goes by, the more I feel sick about it," Hale said. "These people are cold and sick and stuck. As the days go on, and the death toll goes up, how many funerals are we going to go to?"

Joplin Mayor Mike Woolston said Monday night that his community hasn't given up.

"We hope that there are people alive. We have a number of apartment buildings, complexes that are almost completely flattened. So we anticipate finding more people, and hopefully we'll get there in time to find them alive," Woolston said.

Hale said Tuesday that she still hasn't slept since Sunday afternoon, when she didn't know whether her family across town had survived.

"I was hysterical. There's no words to describe not knowing if my family was alive," she said. "The only things left standing in their house was their bathtub and the toilet."

Her mother and grandparents did survive -- by huddling in the bathtub.

The tornado chewed through a densely populated area of the city, damaging or destroying 2,000 buildings, eliminated a high school and made a direct hit on one of the two hospitals in the city.

Based on preliminary estimates, the twister carried winds between 190 and 198 mph, National Weather Service director Jack Hayes said.

More than 1,000 law enforcement officers from four states descended on Joplin to help with disaster response, said Collin Stosberg, a spokesman for the Missouri State Highway Patrol. More than 250 National Guard members were on the scene

Richard Serino, the second-ranking official at the Federal Emergency Management Agency, said President Barack Obama has issued a disaster declaration -- expediting the dispersal of federal resources to the area -- while vowing that "we are going to be here for the long haul."

The flood of aid from strangers and volunteers has helped ease the misery in Joplin.

"I've seen good-heartedness the past 24 hours like I've never seen in my life," Hale said. "As much help that has poured out from the nation, we need. We need the help."

Woolston, the mayor, pledged not to let the tornado ruin his city.

"This is just not the type of community that's going to let a little F4 tornado kick our a**. So we will rebuild, and we will recover."